Abstract:In order to obtain oil-based drilling fluids with stable performance at low oil to water ratios，the stability of water-in-oil emulsions is critical. The effects of emulsifier addition，organic soil addition and temperature on the stability of water- in- oil emulsion with oil-water ratio of 60/40 were analyzed by electrical stability test，static stability test and micro-morphometry. The results showed that when the addition of the emulsifier was 4% ，the emulsion droplets were fine and dispersed evenly，the demulsification voltage was the highest and the emulsion stability was the best. At the temperature of 100 ℃ and 120 ℃，the emulsion droplet size changed little，and the demulsification voltage was close，indicating that there was little difference on stability. However，when the temperature increased up to 150 ℃，the emulsion droplets augmented significantly，the demulsification voltage droped sharply，stability significantly deteriorated. When adding 2% organic soil，the emulsion droplets under 400 times objective lens were invisible to the naked eye，the demulsification voltage exceeded 400 V，and the oil separation rate was only 0.1% after standing for 25 hours，as a result，the stability was remarkably improved. Analyzing the mechanism of key materials and optimizing the amount of appropriate treatment agent were important to ensuring the stability of emulsions with low oil-to-water ratio，which had practical guiding significance for on-site oil-based drilling fluid performance maintenance.

Abstract:The pressure bearing capacity of water-absorbent swelling resin plugging agent was poor，while the single rigid particles of calcium carbonate can't plug well，and their particle size can't match with the size of lost circulation fracture，which can't meet the requirements of plugging in drilling plugging. In this paper，four kinds of resins with particle size（mm）< 1.00，1.00～<2.80，2.80～ <4.75 and 4.75～<8.00 were obtained by polymeration reaction，using acrylic acid（AA），acrylamide（AM）and 2-acrylamido-2- methylpropanesulfonic acid（AMPS）as monomers，N，N- methylenebisacrylamide as crosslinking agent，ammonium persulfate sodium bisulfite as initiator，and the drying，crushing and screening treatment. The resin with 4 kinds of particle sizes was compounded with bentonite，ultra- fine calcium carbonate，asbestos fiber and 5 kinds of non spherical calcium carbonate particles. Through the evaluation of plugging effect of gap plate with gap width of 1—4 mm，the particle size and dosage of plugging material were optimized，and a compound plugging formula was formed. The results showed that the resin particles swelled in 15—30 min， and the absorbency of fresh water and 6.0% sodium chloride solution reached 102—234 g/g and 17—23g/g in 360 min，respectively. The compound plugging agent was diluted with fresh water and polysulfonated drilling fluid，and the plugging slurry with density of 1.37 g/cm3 could completely plug the gap plate with gap width of 1—4 mm，and could bear pressure for 10 min under 6.9 MPa， expressing good plugging effect.

Abstract:In view of the problems of high temperature，high formation pressure and easy lost circulation accident in Ledong block of South China Sea，a plugging slurry with a density of 2.4 g/cm3 was prepared by using composite plugging agent，inducer and suspension stabilizer. The component bearing strength，rheology，suspension stability and plugging effect of the slurry were studied. And the slurry was applied in Ledong block. The results showed that the strength of composite plugging agent and inducer was better，and the crushing rate was less than 25% at 220 ℃ and 50 MPa. The plugging slurry had good rheology，high temperature suspension stability and plugging effect. After aging at 180—220 ℃ for 16 h，the settling rate of the lost circulation slurry was less than 10% after standing for 24 h，and it could filter rapidly within 150 s at 0.69 MPa. When the particle size of sand stone was 4—10 mesh and 10—20 mesh，the percentage of plugging agent invading the sand bed was 65.6% and 52.3% respectively，and the bearing capacity was 10 MPa. After injecting plugging slurry into the wedge- shaped fractures with fracture width of 0.5，1 and 2 mm，a plugging layer with pressure bearing capacity of 10 MPa formed，and the reverse pressure bearing capacity was 7，6 and 6 MPa respectively. The plugging slurry was successfully applied on a well in Ledong block，showing good plugging effect

Abstract:As the oilfield produces in the middle and late stages，the casing pipe is damaged by factors such as formation water corrosion，production perforation，workover operations and cementing quality，which seriously affects the normal production of oil and gas wells. In view of the problems of the commonly used squeezing cement plugging technology for shallow sleeve leakage， which contained solid phase，poor injection capacity and low plugging strength，the bisphenol A epoxy resin DGEBA was prepared by using epoxy resin，diluent and curing agent as raw materials. The performance evaluation results showed that the DGEBA prepared by using n- butyl glycidyl ether（BGE）as diluent at 55 ℃ improved the penetration. The curing agent compounded by aromatic amine and polyamide could adjust the curing time of DGEBA within 3—6 hours. The compressive strength of the cured body was greater than 40 MPa，and it could still maintain 90% strength after aging for 360 days. The plugging pressure could be blocked more than 30 MPa，which met the leakage plugging requirements for shallow casing pipe in Shengli oilfield. By adding micro silicon powder，the shrinkage of the cured epoxy resin could be reduced，and the performance of the epoxy resin system could be improved.

Abstract:In order to meet the rapid，economical，and safe requirments of seal repair in oil and gas wells，a unique pressure activated sealant（PAS）was prepared with carboxylated acrylonitrile butadiene rubber latex（XNBRL），xanthan gum，MgCl2 and alkylphenol ethoxylates. Morphology characterization of sealant particulate was implemented by laser particle size analyzer and microscopic system with super depth of field. The sealing property was studied using a specially designed dynamic sealing detector， the mechanism of pressure activated seal was analyzed，and the field trial was conducted in G2 offshore gas well. The results showed that the prepared PAS was a kind of polydisperse fluid，wherein the solid particles were regular complex droplets with an average size of 261.5 μm. PAS could effectively plug the leaks，e.g. thread and crack under 15 MPa differential pressure，and the sealing capability reinforced with the increase of temperature. The newly developed mechano-chemical coupling model revealed that the complex droplets could be activated by dehydrition effect caused by the differential pressure of leakages，followed by aggregation and fill of active particulates in leak geometry that led to the self- adaptive sealing property. Field trial was further carried out to validate PAS’s application of tubing leak repair in a certain offshore gas well with a sustained casing pressure.

Abstract:In the hydraulic fracturing stimulation measures，the injection of proppant often leads to the problems such as sand out， sand plug or no injection，which affects the fracturing effect. Using the self- assembly characteristic of supramolecular material， supramolecular building unit was synthesized by using N，N- dimethylformamide（DMF）as solvent，adding isocyanurate and tetramethylammonium chloride，and then the phase change fracturing fluid（PCFF）was prepared by modifying the building unit through functional unit，sodium dodecyl benzene sulfonate，polyvinyl pyrrolidone，hydrogen peroxide，calcium chloride，etc. The PCFF and the non-phase change fracturing fluid were mixed and heated to 80 ℃ to prepare a phase change solid. The synthesized products were characterized by NMR and SEM，the microstructure of the system was analyzed，and the injectability of phase change fracturing fluid and the pressure resistance and flow conductivity of phase change solid were studied. The results showed that during the heating process，the molecular self-assembly arrangement of PCFF underwent a phase change and formed a solid. The PCFF had good injectability，and the average viscosity at 20—70 ℃ was only 17.55 mPa · s. The phase change solid had good pressure resistance and crush resistance，and the crushing rate under 28 and 52 MPa closing pressure was 1.83% and 3.22%，respectively. The conductivity of phase change solid under different sanding concentrations was better，and the high-pressure conductivity was close to that of ceramsite and much higher than that of quartz sand. During the fracturing construction process，only liquid was injected. The PCFF formed a solid phase at the formation temperature to support the fractures and established oil and gas channels，avoiding sand plugging and injectability problem of solid proppant.

Abstract:In view of the technical problems such as low viscosity，poor temperature resistance and difficulty in carrying sand in cellulose fracturing fluid，nano hybrid cellulose fracturing fluid（cellulose nano fracturing fluid for short）was prepared by adding cellulose nanocrystals （CNCs） into cellulose fracturing fluid. The dosages of compound crosslinking agent composed of triethanolamine and zirconium butanol and CNCs were optimized. The shear process of cellulose nano fracturing fluid gel in pipeline was simulated by rheometer. The effects of shear rate and temperature on the rheological properties of cellulose nano fracturing fluid gel were studied. The results showed that adding 1000 mg/L CNCs into cellulose fracturing fluid gel could significantly improve the viscosity of fracturing fluid. When the amount of compound crosslinking agent was 0.4%，the viscosity of cellulose nano fracturing fluid gel could reach 600 mPa· s at 25 ℃ and 170 s-1，which was higher than that of blank fracturing fluid gel by 160 mPa· s. After shearing at 120 ℃ and 170 s-1 for 60 min，the viscosity could reach 170 mPa· s and the viscosity increment was 70 mPa· s. CNCs could significantly improve the sand carrying capacity of cellulose fracturing fluid gel. At 25 ℃，the elastic modulus of cellulose nano fracturing fluid was twice bigger than that of blank fracturing fluid gel. CNCs dispersed in the cellulose grid，which could effectively improve the shear resistance and temperature resistance.

Abstract:In order to enrich the gel fracturing fluid system，the new quadripolymer synthesized by methacrylic acid（MAA），2- acrylamido- 2-methylpropane sulfonic acid（AMPS），N，N- dimethylacrylamide（DMAM）and sodium p- styrenesulfonate（SSS） was used as a thickener，and the organic zirconium crosslinking agent was used to crosslink it. The rheological properties of the quadripolymer solution at different concentrations and their cross- linking processes were studied. The effects of shear rate and temperature on the relationship between viscosity and time during cross- linking process were investigated. The rheological properties of polymer crosslinked gel’s breaking processes were studied too. The effects of breaker dosage and temperature on the relationship between complex modulus and time during gel breaking process were investigated. The results showed that the viscosity of polymer solution increased with increasing polymer mass faction at 170 s-1 . The steady-state viscosity of 0.6% polymer solution was 107.7 mPa · s，and the flow curve was conformed to the Cross constitutive equation. The viscosity of cross- linking system decreased with increasing shear rate and temperature. The curve of viscosity varying with time in cross-linking process could be described by 4- parameter cross- linking process model. In the experimental range，the more dosage of breaker and the higher temperature，the better effect of gel breaking process was. The rheological kinetic model of 4-parameter gel breaking process could be used to describe the curve of complex modulus varying with time in gel breaking process.

Abstract:Acid fracturing is one of the commonly used measures to increase production in carbonate reservoirs. The degree of inhomogeneous etch on fracture morphology plays an important role in the conductivity and final effect of increasing production after acid fracturing. With the aim to describe the degree of inhomogeneous etch more comprehensively，the inhomogeneous etch coefficient was introduced to characterize the degree of inhomogeneous etch. Firstly，the point cloud data of core slices before and after acid rock reaction was obtained by three-dimensional laser scanner，and through the software Geomgaic and Matlab the point cloud data was processed and the surface morphology characteristic parameters was calculated furtherly，including the extended interface coefficient in the horizontal direction and the standard deviation coefficient of acid corrosion height in the vertical direction，and the inhomogeneous etch coefficient was obtained by weighted summation. The higher the degree of inhomogeneous etch，the greater the coefficient of inhomogeneous etch. Considering the influence of different factors，the factors was sorted by parameter sensitivity analysis，and the order relationship of primary and secondary influencing factors was obtained as follows： acid concentration（59.94%）＞dolomite content（19.78%）＞rotating speed（14.08%）＞temperature（6.19%）. The proposal of inhomogeneous etch coefficient can provide a possibility for fine quantitative characterization of inhomogeneous etch degree of acid etched cracks，and also point out the optimization direction for acid fracturing design.

Abstract:In order to achieve the goal of high efficiency，fast and uniform acidification，deep plugging removal and prolong the period of acidizing validity，organic polyacid YJS- 1，steering agent GX- 2 and high efficiency corrosion inhibitor GH- X were prepared. Then multifunctional and environmental acid DHS-1 was prepared by mixing YJS-1，GX-2，GH-X，hydrochloric acid， hydrofluoric acid and water. The blockage removal performance，chelating performance，glue breaking property，corrosiveness， steering property of DHS-1 were investigated. Finally DHS-1 was applied on site in Tarim Basin，Xinjiang. The experiment results showed that DHS- 1，whose formula was 10% HCl，2% HF，10% YJS- 1，6% GX- 2，0.5% GH- X，could effectively dissolve the blockage without excessive dissolution and avoid destroying the rock skeleton，and had a good slow performance during reacting with clay mineral. It had excellent performances of strong dissolution，deep penetration，inhibition of secondary precipitation，low corrosion，no residue，effective steering and easy biodegradation. The field application results showed that compared with conventional acidification，the acidification process was simplified，the cost was reduced，the effect of increasing production and injection was obvious，and the average period of acidification was more than 200 days.

Abstract:In order to obtain a suitable high strength plugging agent for tight fractured reservoirs treatment，epoxy resin was investigated in this work. The effects of the diluent on the dilution，ageing time，density，strength and contractility of epoxy resin were studied. The results showed that the absolute ethyl alcohol had a good effect on the dilution，and it also had little effect on the epoxy resin strength. But the excess ethyl alcohol would lead to a high contractility. The diisobutyl phthalate（DBP）was used to combine with ethyl alcohol，and it showed a good performance when the mixed proportion was in range of 1∶3—1∶5，and the setting time was controllable. The addition of the silica fume could significantly improve the setting strength up to 10 MPa，and the contractility was only about 1%—2%，meanwhile，the cured product of the resin plugging agent had certain toughness. Besides， the density of the plugging agent should be adjusted close with the formation water. The plugging ratio could be more than 99%， indicating that the system was suitable to seal large cracks.

Abstract:The reservoir heterogeneity of Suizhong 36-1 oilfield in Bohai Sea is strong and the channeling flow in large channel is very common，which leads to the channeling flow of chemical agents along large channels during water flooding or conventional profile control. In order to improve this problem，polymer pre- crosslinked gel XD with composite crosslinked intercalation was prepared by using sodium bentonite，acrylamide，N，N- methylene- bis- acrylamide，chromium acetate，ammonium persulfate and thiourea as raw materials. The water swelling，viscosify capacity，strength，toughness and profile control effect of XD were evaluated，and the profile control mechanism of XD was analyzed. The results showed that XD expanded when it met with water and had good suspension and dispersion in water. The system had low initial viscosity and good injectability. XD had good water swelling property and controllable expansion time. After a certain expansion time，the viscosity of the system increased. The expansion multiple of XD after steeping 20 hours in formation water at 65 ℃ was about 8. The amide group with absorption ability gradually extended in water，which increased the viscosity of XD surface，but the integrity of the microsphere remained. XD had good strength and toughness before and after expansion. After the injection of XD system，the secondary water flooding could enhance the oil recovery by 15.7% on the basis of the primary water flooding，which met the deep profile requirement of reservoir with permeability greater than 3 μm2 or even higher

Abstract:In order to effectively utilize cotton pulp black liquor and reduce environmental pollution，the black liquor-phenolic resin composite gel was prepared by hydrothermal method with alkaline cotton pulp black liquor，phenol，formaldehyde and polyacrylamide as raw materials. The gel was characterized by FT-IR，TG-DTG and SEM. The effect of phenol addition on the gel was studied，and the salt tolerance，acid and alkali resistance and blocking effect of the gel were evaluated. The results showed that the network of black liquor- phenolic resin gel was compact and the thermal decomposition temperature was 200℃. The gelation time of the gel with 2%—4% phenol addition was 24—14 h，the moisture content was 72%—75%，and the water absorption ratio was 3.60% —3.92% . The gel had the advantages of low viscosity，easy pumping，good salt tolerance，and acid and alkaline resistance. The sealing effect of gel was good. The sealing rate of artificial simulated core was more than 99% . Preparation of plugging agent by black liquor from cotton fleece could not only improve the pollution of black liquor，but also reduce the exploitation cost of heavy oil.

Abstract:In order to meet the sealing requirements of plugging agents under the conditions of unclear fracture scale，complex pore structure，high temperature and high mineralization reservoir in Tahe oilfield，the styrene-modified polyacrylate self-adhesive resin was prepared by suspension polymerization using butyl methacrylate（BMA），stearyl methyl acrylate（SMA）and styrene（St）as monomers，benzoyl peroxide（BPO）as initiator and polyvinyl alcohol（PVA）as suspending agent. The effects of styrene addition on the resin structure，thermal stability，oil solubility and self-adhesive property were investigated，and the plugging property of resin particle was examined. The results showed that the resin had good thermal stability with a thermal decomposition temperature of 302.95 ℃ and a glass transition temperature of 27.8 ℃ when the dosage of styrene was 40%. The resin was completely oil-soluble after soaking 18 hours in diesel oil at 130 ℃. The viscosity of the resin achieved a maximum value of about 105 mPa· s at 110 ℃. Under simulated reservoir condition，the self-adhesive resin exhibited a good sealing pressure gradient of 1.27 MPa/m.

Abstract:Aimed at the problem that it is difficult to simulate the gravity segregation in real reservoir condition by indoor experiments，the gravity segregation physical model in high temperature and high- pressure gas flooding that can stimulated the gravity segregation under reservoir conditions was developed independently. the gravity segregation physical model in high temperature and high pressure gas flooding that can stimulated the gravity segregation under reservoir conditions was developed and gravity segregation was characterized by the produced fluid difference of upper and lower layers，CO2 immiscible flooding using long cores was conducted to study gravity segregation at different injection rates，the gravity segregation degree was evaluated through oil recovery proportion at upper and lower layers of core when gas breakthrough，final recovery and core displacement profiles，and the mechanism that how gas injection rate affected gravity segregation was also analyzed. The results showed that，the gravity segregation was serious that oil recovery of lower layer was nearly zero and oil recovery of top reached up to 97.5% when gas injection rate was at low value of 0.1 mL/min，resulting in the whole sweep efficiency of core was so poor that final oil recovery was only 49.49%. The oil recovery proportion of upper layer reduced to 50.9% as gas injection rate increased from 0.1 mL/min to 1 mL/min，and the final oil recovery even reached up to 60.26%. The residual oil of core displacement profiles decreased since gas injection rate increased，indicated that the gravity segregation degree got weaken. With increasing gas injection rate，CO2 level viscous force increased，the suppression of vertical gravity caused by oil- gas density difference was enhanced，the core sweep efficiency was improved as gravity segregation declined. Experimental results can provide theoretical basis for optimization of CO2 flooding gas injection parameters in low permeability reservoirs.

Abstract:In order to improve the oil recovery of foam flooding，the oil-flooding effect of low salinity water pre-flooding during foam injection was analyzed by indoor core-flooding experiments. The effect of crude oil composition and injected water salinity on oil displacement performance was investigated. The experimental results showed that the wettability of crude-oil aged oil-wet core appeared to be water wetting characteristic by low salinity water flooding. The core was flooded by the simulated formation water with a salinity of 130000 mg/L until the water cut was 98%，and then 2 PV of low salinity water with the salinity of 2784 mg/L was injected，and then 2 PV of nitrogen and foaming agent solution of 0.1% mass fraction was injected alternately in which the volume flow ratio of the gas/foaming agent solution was 1∶1. The maximum plugging pressure of foam flooding was 0.242 MPa. Enhanced oil recovery by up to 14.20% was observed with foam flooding after low salinity water flooding compared to water flooding. Low salinity water flooding and foam flooding could have a synergistic effect. The subsequent foam flooding process after low-salinity water flooding generated stable foam，which improved the foam's plugging ability in porous media，thereby greatly improving oil recovery. As the acidic contents of crude oil and the salinity of injected water decreased，the rock would be more hydrophilic and had better foam flooding performance.

Abstract:In order to improve the oil recovery of low permeability reservoir，active water imbibition huff and puff technology is widely used in horizontal wells after fracturing，and the key to its success is to develop a high-efficiency imbibition agent formula. In this paper，a low interfacial tension anion-nonionic surfactant，tristyryl polyoxyethylene ether sodium hydroxypropyl sulfonate （TPHS）was developed by "one pot boiling". The interfacial tension and salt resistance performance of HPHS was investigated. A low interfacial tension nano fluid，composed of TPHS，AOS and nano- SiO2 particles，was optimized by contact angle test， spontaneous infiltration test and forced infiltration test，and the displacement evaluation was carried out. The results showed that the interface tension between TPHS solution and the crude oil could still be kept at 10- 1 mN/m at the temperature of 80℃ and at the salinity of 300 g/L，exhibiting good salt and temperature resistance. The interface tension between the complex system of 0.1% TPHS+0.2% AOS and the crude oil decreased to 10-2 mN/m，which was helpful to displace crude oil in small pores. The addition of a small amount of nano- SiO2 particles（0.05%）could produce synergistic effect of wetting with TPHS and AOS，which could improve the imbibition rate and enhance the recovery rate by 12.7%，compared to that of the surfactant flooding. At the same time， the emulsion stabilized oil wall could be formed and the anhydrous oil recovery period could be prolonged. It was confirmed that the addition of nano-SiO2 to surfactant mixtures resulted in enhanced imbibition oil recovery in low permeability reservoirs.

Abstract:According to the development demand of low-permeability reservoir in Xinjiang oilfield，the performance evaluation of nano displacement agent iNanoW1.0 was studied by conventional measurements of the surface/interfacial tension，wettability，clay expansion and core displacement experiment. The results showed that the surface/interfacial tension and wettability of nano displacement agent iNanoW1.0 were similar to that of water. The capillary rising height experiment showed that，iNanoW1.0 could reduce the interaction between water molecules and reduce the starting pressure. iNanoW1.0 could improve the anti-swelling effect of clay swelling inbibitor，which was helpful for the development of water sensitive reservoir. Core experiments showed that the nano oil displacement agent iNanoW1.0 could realize the permeability of water in low permeability core，while water without nano oil displacement agent could not pass through the core.

Abstract:In order to meet the requirement of tertiary oil recovery technology under the condition of high temperature and high salt reservoir in Hade oilfield，Pickering emulsion template method was used to modify SiO2 nanoparticle with aminopropyl triethoxysilane and perfluorooctanoic acid，and amphiphilic nanoparticle with hydrophilic amino group and hydrophobic fluorocarbon chain was prepared. The effects of temperature and the concentration of Na+ and Ca2+ on the interfacial tension between amphiphilic nanoparticle dispersion fluid and simulated oil were studied. The migration law of nanoparticle in porous media and the performance of oil recovery were investigated. The results showed that the amphiphilic nanoparticle had good salt tolerance and temperature resistance. The dosage of Na + and Ca2 + and temperature had no significant effect on the interfacial activity of amphiphilic particle，and the interfacial tension between amphiphilic nanoparticle dispersion fluid and simulated oil maintained at the order of 10- 2 mN/m. Although the amphiphilic nanoparticles adsorbed on the pore surface of core，which slowed down the migration rate of some particles in amphiphilic nanoparticle dispersion fluid，desorption and migration of the core could be realized through Brownian motion. The final adsorption capacity of amphiphilic nanoparticle in porous media was less than 10%，showing excellent adsorption resistance. Amphiphilic nanoparticle could improve oil recovery under the condition of high temperature and high salt. Under the condition of 120 ℃ and salinity of 215 g/L，the recovery factor increased by 10.1 percentage points over water injection after 0.5 PV 0.6% amphiphilic nanoparticle dispersion solution was injected. Amphiphilic nanoparticle combined the advantage of molecular surfactant and homogeneous particle，and had good interfacial activity and stability.

Abstract:Polymer- surfactant agent is characteristic of good viscosity increasing and emulsifying properties，it is necessary to analyse the cause that the production wells were of high emulsification ratio and prominent effect of emulsification in the field test of polymer- surfactan flooding after polymer flooding. The effects of different oil- water ratio，salinity，oil composition and concentration of polymer- surfactant agent on the properties of emulsion were studied，and the law of migration of emulsion produced by polymer-surfactant agent was analyzed through long core flooding experiments. The results showed that the polymer surfactant agent had emulsifying ability during polymer- surfactant flooding due to the surfactant interface activity and steric hindrance effect. When the concentration of polymer- surfactant agent reached up to the critical associating concentration，the emulsion stability further increased，and the emulsification phenomenon was more serious when the gum and asphaltene of the crude oil was higher. While，the salinity had little effect on the emulsification. Compared with polymer，the polymer- surfactant agent had a more uniform concentration distribution in the core，and the piston propelling effect was obvious. In the high permeability core，the polymer-surfactant agent could realize the emulsification at the initial stage of injection，producing time was of 0.2—0.8 PV. In the low permeability core，the emulsification became more obvious at the later stage of injection，and producing time was 0.5—0.8 PV. The emulsification type of the whole process was light and moderate oil-in-water emulsification，and the emulsification sealing position was about 58%—75% of the injection. Therefore，the fracturing time should be designed with the change of injection pressure during the emulsifying sealing，with a radius of at least 1/4 well spacing. The EOR was more than 2.5% through well-timed fracturing initiation.

Abstract:In order to explore the effects of inorganic salts on the rheological properties of anionic Gemini surfactant（GACS416） solution and its mechanism，the influence of inorganic salt type and concentration on the viscosity and viscoelasticity of surfactant solution were measured by DV2T viscometer and MCR 301 interfacial rheometer. The dimensional variations of micelles were studied by dynamic light scattering technique. The experimental results indicated that after adding NaCl and KCl with appropriate concentration，the viscosity of GACS416 solution could be effectively increased，while MgCl2 and CaCl2 has no viscosification effect. With the increase of NaCl concentration，the solution viscosity first increased and then decreased，while the elasticity first weakened and then strengthened. The solution viscosity and viscoelasticity of the solution were the best when the NaCl concentration was 500 mg/L. With the increase of KCl concentration，the viscosity of the solution increased first and then decreased，and the elasticity increased continuously. When NaCl or KCl concentration was lower than 1000 mg/L，the viscosity of the solution could be increased effectively. The microstructure of the solution demonstrated that with the increase of NaCl concentration，the average hydraulic radius of micelles in GACS416 solution first increased and then decreased，and the viscosity and elasticity of the solution first increased and then decreased. However，with the increase of KCl concentration，the average hydraulic radius of micelles gradually increased，and the viscosity and elasticity of the solution also increased correspondently. The solution viscosity and viscoelasticity were the best when the NaCl concentration was 500 mg/L or when the KCl concentration was 1000 mg/L.

Abstract:It is very difficult for the conventional polymer flooding agent to meet the requirements of temperature resistance，salt tolerance and long-term aging thermal stability. The water-soluble hydrophobically associating polymer（PSA）was prepared by the copolymerization with acrylamide（AM）using N-phenethyl-N-dodecylmethacrylamide（PEDMAM）as associative monomer and 2- acrylamide- 2- methylpropanesulfonic acid（AMPS）as functional monomer. In addition，the comprehensive properties of PSA prepared at an optimum monomer（AM∶AMPS∶PEDMAM）mass ratio of 83∶15∶2 were investigated. The results showed that， compared with partially hydrolyzed polyacrylamide（HPAM），PSA had good tackifying capacity，temperature resistance，salt tolerance，shear resistance，aging stability and oil displacement performance. Under the condition of 85 ℃ and 32 g/L salinity with 800 mg/L the mass concentration of Ca2+ and Mg2+，the viscosity of 1500 mg/L PSA solution was 16.3 mPa· s，and the retention rate of viscosity was more than 80% after anaerobic oxygen aging for 60 days at 85 ℃ . Moreover，the results of laboratory core displacement experiment showed that 0.7 PV 1500 mg/L PSA could further enhance the oil recovery by 35.05% over water injection，which was greater than that of 3000 mg/L HPAM with similar viscosity by 12.35 percentage points. PSA had significant advantage in oil displacement.

Abstract:In order to study the relationship between emulsification and enhanced oil recovery（EOR）of surfactant/polymer complex flooding system with different emulsion，the emulsion characteristics of on-site production fluids of Xinjiang oilfield was analyzed，and the displacement efficiency of the surfactant/polymer complex flooding system was tested，and the migration rule of the emulsion and the contribution of emulsification to enhanced oil recovery were determined. The results showed that the low viscosity emulsion exhibited elasticity at low shear rate，and viscosity at high shear rate. The high viscosity emulsion mainly exhibited viscosity at low and high shear rate. The flooding results showed that the emulsion stability was poor at the early stage of emulsification. At the middle stage of emulsification，the concentration of the chemical agent was higher and the particle size of the emulsion changed well，hence，there existed a compensation of emulsification on the viscosity of oil flooding system. At the end of emulsification，the concentration of chemical agent was lower，the emulsion drop was less，and the degree of emulsification was weaker. When the core permeability was less than 100×10-3 μm2，the enhanced oil recovery increased first and then decreased with the increased of the emulsification comprehensive index（ECI），and the optimum ECI was 55%. When the core permeability was more than 100×10-3 μm2，with the increase of ECI，the enhanced oil recovery increased gradually，and the optimum ECI was 88%， and the contribution of emulsification to enhanced oil recovery was 8 percentage points.

Abstract:In order to solve the serious scaling problem of water injection system in Jiudong oilfield，the scaling cause of injection water（K1G1 mixed with produced water from K1G3 reservoir）in Jiudong Oilfield was studied，the effect of 7 kinds of scale inhibitors on calcium carbonate scale and calcium sulfate scale was evaluated，and the crystal structure of scale was observed by scanning electron microscopy（SEM）. The results showed that the scaling type of the injection water was calcium carbonate，with a small amount of calcium sulfate scale. The scale inhibition effect of polyaspartic acid（PASP）was the best. it was found that the carboxylic acid anion contained in the molecular structure of PASP could react with Ca2 + to form soluble chelating molecules in water，and PASP adsorbed on the surface of the crystal，which reduced the intermolecular force and destroyed the crystal structure， as a result，the crystal morphology was aberrated and the formation of crystals was effectively prevented. By adding PASP into the injected water in Jiudong Oilfield，the scaling problem of produced water reinjection could be solved.

Abstract:In order to improve the oxidation desulfurization（ODS），an amphiphilic heteropolyacid catalyst CTAPW was prepared with hexadecyl trimethyl ammonium bromide（CTAB）and phosphotungstic acid. The product structure was characterized by infrared spectrometer and X- ray diffractometer. And the optimum reaction condition of the catalyst was investigated by desulfurization experiment of simulated oil. The results showed that under the optimum condition，such as 60 ℃，0.8∶1 mass ratio of CTAPW to sulfur content in simulated oil，6∶1 molar ratio of H2O2 to sulfur content，1 h reaction time，the desulfurization rate of simulated oil containing dibenzothiophene with an initial sulfur content of 500 mg/L was 96.3%. The catalytic oxidation system had wide applicability to different sulfur- containing compound oils，and the desulfurization rate of simulated oil containing benzothiophene or 4，6- dimethyldibenzothiophene reached more than 90% . CTAPW was an ideal amphiphilic catalyst. The introduction of long- chain alkyl groups（C16）made the catalyst have good emulsification and dispersion ability. Therefore，a relatively stable W/O emulsion was formed，which promoted the effective oxidation and separation of sulfur in oil phase.

Abstract:In the study of air injection technology for enhancing oil recovery，the kinetic parameters of crude oil oxidation are not only basic data，but also can evaluate the feasibility of this technology in the field project application. In order to clarify the oxidation kinetics of crude oil，the accelerated calorimeter method was used to study the oxidation characteristics of crude oil under high pressure adiabatic condition. The results showed that the ignition temperature of crude oil could be determined by accelerated calorimetry experiment，and the mathematical model of oxidation kinetics of crude oil could be deduced after the experiment data was processed by using kinetic theory. After the calculation method of kinetic parameters was obtained，the activation energy and pre-exponential factor of crude oil could be calculated. Compared with the conventional methods such as thermogravimetric analysis and differential scanning calorimeter，the accelerated calorimeter method was more close to the actual formation condition，and the determination results of crude oil oxidation kinetic parameters were more accurate，which had good promotion value and application prospect.

Abstract:Volumetric fracturing is the main stimulation process for unconventional oil and gas production. Because of high pump speed，large fluid volume and large displacement，the fracturing fluids are required to possess the properties of continuous mixing， low friction and high flowback rate. Therefore，the "slickwater" fracturing fluid system is demanded. The core component of slickwater is polymer drag reducer，which directly determines the performance of slickwater. In this paper，the recent progress in the field of drag reduction in terms of drag reducer properties，drag reduction mechanism，effecting factors of drag reduction performances，were reviewed. The application situation of drag reducer in slickwater hydrofracking for unconventional oil and gas production were introduced. Finally，the future trends in developing polymer drag reducers were outlooked.

Abstract:The stability of emulsions presents a significant challenge in surface process particularly，both in terms of crude oil dehydration and produced water treatment. Considering the potential influence of asphaltene and resin in crude oil，especially the polymer and surfactant would be appeared in actual produced emulsions in chemical flooding process. This paper reviewed the application and research progress of molecular dynamics simulation in the field of oil- water interface stability mechanism. The available methods and relevant software for characterizing the visualization，density distribution，radial distribution function，oil water interface formation energy，and molecular diffusion coefficient were discussed，respectively. In order to understand the interphase interaction of crude oil emulsions and address it，the molecular dynamics simulation could be used as an effective method according to the existed research. The review indicated that breaking through the limitations of model simplification and single factor simulation to understand the molecular adsorption，droplet coalescence，and droplet separation from micro-scale was a research application and development direction of molecular dynamics simulation in the fields of oil- water emulsification and demulsification. Furthermore，the component properties of internal phase and external phase，and the temperature and pressure conditions need to be considered.

Abstract:The foaming agent drainage of gas well is an important measure to improve the production per well，and it is also one of the most common and economically viable methods for drainage of gas wells at home and abroad. Based on the domestic and foreign literature research，the mechanism of foaming agent was analyzed，the application progress，advantages and disadvantages of various types of common foaming agents were summarized. And the research progress of new foaming agents with temperature resistance，salt resistance，acid and alkali resistance，H2S resistance and condensate resistance was introduced. The existing problems in the preparation and field application of foaming agents were analyzed，and the development trend of foaming agents in the future was put forward.

Abstract:Bohai oilfield had achieved some results of increasing oil production and decreasing water cut after polymer flooding enhanced oil recovery technique was implemented since 2003. But the increasing scale of polymer flooding brought many challenges to the treatment of crude oil and water on platform. The problems on oil- water separation of polymer- containing produced fluid，treatment of polymer-containing wastewater，treatment of oily sludge and wastewater reinjection were analyzed，on the basis of the status of produced fluid treatment in offshore polymer flooding oilfield. Studies on the treatment of polymer-flooding produced fluid in rencent years had significant instruction for the development of demulsifiers，water clarifiers and plug removal agent in offshore polymer flooding oilfield. The recommendations concerning further improving the processing capacity of polymer flooding produced fluid，enhancing the treatment effect of crude oil and wastewater，reducing the amount of oily sludge and increasing the efficiency of removing plug of oil or water well in offshore oilfield were provided.